On the basis of comparative morphological studies, correlating surface topography with established function, and on the basis of combined electrophysiological and morphological studies where function is not well established already, we hope to be able to draw strong inferences concerning the transduction processes in the vetebrate vestibular and auditory receptors. Scanning electron microscopy will be used to develop maps of receptor polarization and topographical types, and intracellular stains and other methods will be used to trace VIIIth-nerve units of observed function back into the mapped regions. In order to clarify the roles of the stereocilia and kinocilia in transduction, we will observe not only their correlations with specific sensory modality, but also their structural relationships with the gelatinous superstructures of the inner ear, and their comparative morphology from species to species and in a given species during development and growth. Among other things, we plan to test the hypothesis of compliance anisotropy in the stereocilia array and its postulated role in establishing functional polarization for receptor, the hypothesis of a place principle within an anuran auditory papilla, and several hypothetical relationships between frequency sensitivity and ciliary-array topography.